Don't answer a number you don't recognize. If it's legitimate & important, they'll leave a message. By picking up an unknown call, you're just proving that your number is "live", & the scammers will sell it to other scammers, & you'll just get more & more calls. And for jeebus sake, don't call an unknown number back! You don't know what you could be getting into. Scammers are lowlifes, but they obviously have the technology to do bad things. If everybody would simply not answer unknown calls, they'd be out of business.